The disclosure relates generally to inspection of machine components, and more particularly to inspection of components of a dynamoelectric machine, such as an electric generator, at least partly immersed in a fluid in a sealed chamber, such as a sealed casing.
Dynamoelectric machines can include sections that are difficult to access, but that include components that require inspection. Some such machines include areas that are immersed in a fluid or otherwise require isolation from atmosphere, which further impedes access for inspection and/or maintenance. For example, some electric generators include a casing filled with a coolant in which the rotor of the generator rotates. The coolant typically must be kept in the casing because it would be contaminated should air enter the casing or might have an effect on surroundings should it escape. This is particularly true of hydrogen cooled generators, where hydrogen gas fills the generator casing, usually under pressure, to cool the windings and/or magnets and/or other parts of the generator.
To inspect components in such a machine typically requires shutting down the machine, draining the fluid, and disassembling the machine at least as far as inspection can be performed, reassembling the machine, and recharging the casing with fluid before restarting the machine. In the case of hydrogen cooled generators, care must be used to contain and/or dilute the hydrogen to avoid fire/explosion hazard during draining and recharging of the casing. The process can be time consuming and expensive.
The problem of inspection that can require time consuming and/or expensive disassembly and reassembly is not unique to dynamoelectric machines, and, as a result, inspection apparatus have been developed to inspect many devices, machines, and/or installations. Of particular interest with respect to embodiments of the invention disclosed herein, borescopes are used to inspect portions and/or components of turbomachines that would otherwise require disassembly of the machines. A typical borescope includes a head on the end of an elongated support structure. The head can capture an image that can be viewed by a user. For example, the head can include a lens that can transmit the image to a viewer or eyepiece or the like via fiber optic cable extending through the support structure. Alternatively, the head can include a camera that can transmit a captured image to a display via signals carried by an electrical conductor in the support structure and/or electromagnetic radiation. The support structure is typically a tube or concentric tubes in which optical fiber, electrical conductors, cables, and/or other components extend from a control box to the head. Rigid borescopes typically employ a tube that is resistant to bending. Flexible borescopes typically include a flexible tube, which can be made from a tube of flexible material and/or can be a composite of joined segments of material. Controls on the control box can be used to adjust the orientation of the head and/or tube, to activate lighting, and/or employ other features of the borescope.
To accommodate inspection with borescopes, turbomachine casings can include a plurality of access ports sealed with borescope plugs or the like to seal the access ports when no borescope is present and/or between inspections and/or uses of the ports. In addition, borescope mounts have been used to support and/or enhance operation of borescopes, such as by allowing a borescope to swivel in place to increase a viewable area, and/or using a guide tube to conduct a borescope through layers of casings or the like to an inspection site. However, the machines in which these are installed and/or used can typically be depressurized and/or shut down to allow swapping out of a port cover for a borescope or the like with relative ease and without significant passage of fluid through the port. Thus, these solutions typically are not suited for use in a machine whose casing is sealed and contains fluid that should be kept within the casing, particularly pressurized gas, even when shut down.